Demented Debra's Darkness
by PakaluPapito'sFanboy
Summary: What if killing LaGuerta left Debra even more ruined than it did? What if it left her with the urge for blood? A Dark Passenger? Debster fic. Rated M for violence, Deb's potty mouth, and possible future lemon.
1. Chapter 1

"Deb," he uttered in surprise as he crouched in front of LaGuerta's unconscious form.

She stared at the sight in front of her in disbelief, her gun pointed at the ground, "Oh god. Dexter." She aimed the gun at her brother as he stood up and walked over to the barrel where he had placed his knife.

The knife he was going to use to kill the police captain. "Deb, you shouldn't be here."

"W-Why… shouldn't I be here?" Debra asked, her voice trembling slightly in fear. Fear of what Dexter was about to do. She knew, but refused to believe it. Tears began to well in her eyes as she glanced towards LaGuerta, who was still out. "What're you doing?"

"What needs to be done," he said. ' _What needs to be done to protect you._ '

Debra whispered, "Are you gonna kill her?"

"You need to leave, I need to finish this."

She looked at him with pleading eyes and voice, "Dexter, you can't."

"I can, and I will." Dexter might have let LaGuerta go if Debra wasn't involved in this. But she was. He was doing this for her.

Deb panicked, a nervous an uneasy smile on her face, "Jesus, fuck, no Dexter! You can't do this!"

A soft and short moan was heard behind him as both of them turned their gaze towards the now awake captain. Dexter turned towards her, "It's the only solution, the only way to end this."

"No, no, no, I can't let you go through with this!"

"Shoot him, Deb." LaGuerta suddenly said, her voice weak and exhausted. Dexter looked between the two of them, unsure of what Debra would do. "You have to end this. Shoot him."

Dexter's hand hovered over the knife before he gripped it. Debra noticed and quickly pointed her weapon back to him, "Stop!" He did.

"Do it, Debra. Shoot him." She glanced between the two, dreading the choices she had.

"Shoot him! This is not who you are. You are a good cop. You're a good person, you're not like him."

She sobbed lightly.

LaGuerta finally shouted, "Put him down!"

Dexter stared at his sister. Maria was right. She was so much better than him. And even though he never deserved her, he still had her. For his entire life, he had Debra Morgan. The kindest person he knew. A paragon and an example. Someone Dexter would have wanted to be like if he was ever to be normal.

And he had taken her for granted his entire life. He never truly realized how lucky he was.

He didn't deserve her.

"She's right," he stated. Debra looked at him in surprise. "It's true, everything she said. You're a good person… The best I know. It's okay." He threw the knife on the ground beside him before spreading his arms to his sides, as if inviting her to shoot him. "I should have died a long time ago… in that container with my mother."

Debra stared at him in disbelief. "No, no, don't say that, Dex! Jesus fuck!" How could he say that? Where would she be if it wasn't for him?

Dexter knew she was wrong. He never should have survived what he saw. He should have died. His death was long overdue, and if someone was going to do it, he'd like it to be Deb. "Do what you gotta do."

She sobbed again, this one jarring through her entire body. She couldn't. Not even if she wanted to. She couldn't kill her protector.

Not after he killed for her.

* * *

 **Several days ago**

Dexter stared at Hannah as she slowly walked towards him. "Stay with me tonight," she whispered, placing her hand on his shoulder.

"No, I can't. I have something to do."

"You're going to visit Debra?" she asked with a false sympathetic smile. Dexter looked her in the eyes. She was lying to him right to his face. Pretending as if she didn't try to kill one of the most important people in his life. He shook his head. "Estrada?"

He shook his head again, his own false smile matching hers. "No, I postponed the deal with him. There's something else that needs to be done." He leaned to kiss her on her neck.

She giggled. "Be careful, naughty boy. Don't want Santa to give you coal for Christmas, do you?" She closed her eyes and leaned her cheek against his, exposing her neck. A perfect opportunity for Dexter. He slipped the syringe into her neck and she fell limp into his arms, "Wha- Dex…"

 **-oOoOoOo-**

Dexter watched Hannah stir back into consciousness with a soft groan. She slowly began to realize where she was. Wrapped in plastic on a table, surrounded by plastic sheets and naked. Realization replaced confusion, "Dexter..?" She swallowed as tears began to form in her eyes.

He finally appeared in her line of vision. He wore the very same apron as last time. Why would he do it again? He seemed… sad, but not regretful. He knew he had to do this.

"Why are you… doing this?" She suddenly gasped as she felt the scalpel cut into her cheek.

"I promised her I wouldn't do this again. But I need proof." He sounded so cold and detached as he placed the blood on the slide and put it in his pocket.

She stared up at him in confusion, her cheek stinging, "Why, Dexter?"

"For my sister's safety." He stated. He walked out of her vision before returning with a knife in his hand, "I already killed my biological brother for her. What's one more person I like?"

"Dexter, I don't-"

He interrupted her, his voice still as cold. "She will never be safe as long as you're free to walk the streets."

She tried to protest again. "I didn't do anything-"

"I tested her water bottle. Anxiety drugs were dissolved into it."

She scoffed, tears coming out of her eyes, "You think I ha-"

"Stop lying!" he almost yelled, causing her to flinch. "It doesn't matter, there's no turning back from this. You might as well confess, since I'm doing this either way."

She stared at Dexter, tears pouring uncontrollably, "I… I did it for us. She wouldn't let you go." She pursed her lips together before uttering, "I love you, Dexter. I pro-"

Her voice stopped as she gasped, the blade piercing through plastic and flesh. She stared pleadingly into his eyes. But it was too late. A single tear escaped from Dexter's eye as he closed them. He couldn't watch her pleading eyes as all light faded from them.

He finally let out an anguished breath before backing up against the wall, staring at her lifeless corpse. His eyes wandered to the bone saw he placed on the table next to his other knives.

 **-oOoOoOo-**

He opened the door to Debra's house, his sister following behind him, as they entered. He placed his bag on the couch table and Debra closed the door. She walked over to the sofa before sitting on it. There was something off about Dexter. He was unusually quiet. He almost seemed sad. It made Deb want to embrace him.

She stared at the ground in front of her. "You barely said two words on the ride home."

He stared at his sister's knees before saying, "I have something for you."

She looked at him, "A present? A new car, I hope."

He shook his head slowly, "No. Something… more important." Her eyebrows furrowed in confusion. "Close your eyes."

She complied. "Hold out your hand." She did rather hesitantly at hearing the sadness in his voice.

She felt something cold and small fall on the palm of her hand. She opened her eyes to see a bloodslide. Her eyes widened, "What the fuck?" She looked up at him, lips shaking, "D-Dex… What- Who… Who the fuck is this?"

"…Hannah McKay."

Debra breathed out a shaky breath, "Th-… That's Hannah?" He nodded. "Jesus Christ, Dexter. Did you… Did you kill her for me?"

He stared at her, "I had your water bottle tested. She dissolved your pills into the water."

She scoffed, voice quiet and trembling, "You killed someone you loved for me?"

He slowly wandered to the sofa opposite of hers and sat down, "I had done it before, I did it again, and I would do it a thousand times over if it meant you'd be safe."

Debra stared at him before swallowing the lump in her throat. "What do you mean… you've done it before?"

His eyes widened ever so slightly. His tongue must have slipped. He sighed. "Remember Brian? My brother?"

She stared into his eyes for a few seconds before realization hit her. "You killed Rudy? Why..?"

He hesitated, "He… He knew he could never replace you while you were still alive. He told me who he was, all the hookers he killed were set up for me. He wanted his baby brother back. But he couldn't, not while you were alive."

Deb's eyes were wide, her lower lip trembling, "And you killed him? Despite knowing he was your brother?"

Dexter smiled softly and sadly, "He accepted me for what I was. But there was something he didn't know."

"What?"

He stared at her, smile widening slightly, "There is no Dexter without Debra. You are one of the most important things in my life. You and Harrison are the only bits of humanity left in me. Without you… I'd be hollow. I wouldn't feel anything. Not even anger. Just an empty shell."

She looked at him, eyes filled with emotion, the most evident being adoration, "You killed your brother who accepted the darkness in you for a sister who didn't even know you? Why? I don't understand."

Dexter stood up, hands in his pockets, "You… You accept the darkness in me. Brian wanted the darkness only. But unlike him, you see the light in me. You bring it out- No… You _are_ the good in me. You accept both sides, and you've struggled and sacrificed a lot of what you believe in to accept me. It was easy for Hannah. Lila wanted only the darkness and Lumen needed it. But you accept the whole me."

She stared at him, heart racing. He continued, "You don't only accept the dark passenger or the mask I put up. You accept Dexter Morgan."

"B-but you killed Brian before I even knew about your darkness."

"Like I said. Without you, I'd be hollow."

She stared at the ground. She was speechless. She finally whispered, "Thank you…"

Silence fell over them for a while. Dexter finally broke it, "Don't mention it."

He turned to leave. A smile on his face.

His sister was safe.

* * *

 **Present**

Debra couldn't. He sacrificed so much for her. He killed for her.

Now it was time for her to kill for him.

She sobbed before tilting her head to the side, eyes blurry from tears that threatened to pour like a waterfall from her eyes, "…Dex…" She needed to see him. She needed to know he was there for her, that she wasn't alone. She couldn't be alone. Not after what she was about to do. She aimed her gun at LaGuerta.

And she pulled the trigger. Dexter jumped and looked behind him in shock and surprise as his eyes took in the sight of LaGuerta's bloody blouse, and closed eyes. He heard the clatter of Debra's gun against the ground and saw her running towards the captain's body before hugging the body tightly. As if it would pull her from this nightmare, undo everything and make things go back to the way they were.

She sobbed into LaGuerta's shoulders as she let out every single tear from her eyes. She felt Dexter's comforting hands on her shoulders. She pulled away from Maria's body, sobbing, before tightly hugging Dexter. She held onto him for dear life and let out her tears again as he ran his hand through her hair gently. She cried for what seemed like an eternity before she fell silent, her chin resting on his shoulder.

She lifted her uninjured hand behind Dexter's head to see LaGuerta's blood covering it. Crimson red. Debra suddenly saw something she never hoped she would see as she stared blankly.

She saw blood trickling down the back of her eyelids. The trickle became a stream. The stream became a flood of red. It filled her up. Suddenly the blood isn't red anymore. It turns pitch black as she closes her eyelids. She suddenly felt a pressure on her head. It felt like her head was about to explode.

And so, Debra Morgan's Dark Passenger was born.

* * *

 **Author's Note: Dun, dun, DUN! What did you think? Did you like it? I hope so. Either way, this fic is going to be a Debster fic. Finally Dexter will take on a pupil that won't betray him. There isn't really much to say except that this is my first fic. I've been reading for a while and decided to try my own hand at this.**

 **Leave a review, Favorite and follow this story if you like it so far.**


	2. Chapter 2

Debra stared forward in disbelief. Dexter was inside the container, fabricating evidence to make it look like a shooting between LaGuerta and Estrada. He told her to wait outside, and she did without saying a word. She was broken. The feeling she had was exactly the way Dexter described his urge. This couldn't be happening to her. She's a monster. Dexter said he deserved to die, but he's wrong.

She does.

He finally came out of that goddamn container and they made their way to the party once again. Along the way, she called Batista, telling him that he couldn't get a hold of LaGuerta and that she stopped looking and decided to make her way back. What truly disturbed Dexter was her voice. It was completely devoid of emotion. Even as they passed through the crowd at the party, her eyes were dead. Staring forward into nothingness. It tortured him inside to know that he was responsible for this.

After the party and the hollow celebrating, they made their way to Dexter's apartment.

Dexter opened the door to see Jaime in the kitchen cleaning Harrison's empty bowl.

She turned around with a tired smile on her face, "Hey!" She put the bowl on the side of the sink before grabbing a towel and wiping her hands, "I put Harrison to sleep just before you came back. I decided to clean the dishes before leaving."

"You could've just used the dishwasher."

"Yeah, but it was only a few plates and a bowl."

"Thanks," he muttered.

Debra finally walked in and was greeted by Jaime, "Hi, Deb."

She simply waved, "Hey," before making her way to the couch.

The babysitter stared after her before looking back at her boss. Dexter quickly covered, his false smile forming, "She's exhausted. A few too many beers. You know Deb."

She smiled and nodded, "Yeah. Anyways, happy new year!" She moved past Dexter and grabbed her purse before making her way to the door.

"Happy new year."

Jaime closed the door behind her and Dexter immediately turned around to see Deb staring blankly at a movie playing on the TV. "Could you get me a beer?"

He had to stop himself from smiling in relief. Finally she said something to him. "Of course." He took a couple of cold ones out of the fridge before sitting down next to her. He handed one to her and placed the other on the table. She said nothing as she opened it and drank. She kept staring at the TV screen, but didn't seem to react to anything happening.

After a while, she just turned it off and kept staring. It took a lingering silence before Dexter could muster up the courage to talk.

"Why didn't you kill me?" She scoffed, not meeting his eyes as she took a gulp of beer. What a stupid question. "I don't deserve you."

She slowly turned to look at him, "Don't fucking say that."

"But it's true," he insisted. "Look what I made you do. You went against everything you believed and killed an innocent person. It's broken you, Deb."

Debra felt anger as she almost slammed the beer bottle on the table, "And you killed your own brother and the woman you… loved… for me. Both of which would have accepted who you are without hesitation." He pretended not to notice her hesitation to refer Hannah as someone he loved.

"But I'm a monster, I deserve death. LaGuerta didn't. It broke you."

She glared at him furiously, "Stop saying that, asshole! You think I would've been any less broken if I killed you!?" Dexter said nothing. Instead, he stared at her. She looked away and muttered quietly, "At least now I have someone who can help me."

He leaned forward and looked into her eyes in confusion, "Help? With what?" She didn't meet his eyes, only staring at the beer bottle she'd placed down. He grabbed her shoulders, "Deb, help with what, what's wrong?"

She swallowed the lump in her throat. "Dex… I'm fucking broken. Ruined. I… I'm completely fucked."

Genuine concern flashed in his eyes as he grabbed her chin and forced her to look at him, "Deb, what do you mean?"

She smiled sadly, tears welling in her blank eyes, "Look into my eyes, Dex. What the fuck do you see?"

He did so. He stared until he suddenly recoiled in horror and realization. He recognized those eyes. Those were the same eyes he had when his dark passenger's urge was potent and pressing. "No. No, no, no!" He finally did it. Harry warned him, but he didn't listen. He finally ruined Debra. Poor, perfect, innocent Debra. Ruined and left with nothing but the very same darkness that haunted Dexter for his entire life.

"I'm… fucked up, Dex. This feeling I have… This urge. It's like you said. I just wanna open the floodgates, b-but I don't know how."

"NO!" He shouted, standing up abruptly as he paced back and forth from the couch to the computer table. He gripped his head in frustration at himself. He finally fucking destroyed her.

"I'm a fucking murderer, Dex. It's happened and there's not a goddamn thing we can do about it. This darkness can't go away just like that. You _know_ it. You tried and it didn't work." She chuckled humorlessly as she looked down, "I'm a goddamn monster."

He placed his arms on the counter in his kitchen before burying his head between them. After a lengthy silence, he finally stood straight and walked towards her, "No, it doesn't have to mean you need to kill, that you're a monster like me. You just need to let it out. Let out the anger, the sadness, everything! Just let it out on me!"

"What're you saying?"

"Vent, that's what I'm saying. Let out everything on me. It's okay. It's the least I could do after what you've done for me. Just open the floodgates."

She stared at him before standing up in front of him, lips trembling and voice whispering, "Are… are you sure?"

He nodded before spreading his arms the same way he did in the container, "Do what you gotta-"

A sharp pain in his cheek suddenly jolted through his nerves as Deb's fist connected with it. His head snapped to the side and he staggered backwards, holding his cheek and clenching his teeth to stop any noise from coming out of his mouth. "Alright… How are you fee-" He suddenly exhaled all breath in his lungs sharply as Deb punched him in the gut. She followed up with another to his abdomen and finally finished by slamming her fist into his chest.

Dexter gritted his teeth, trying not to express the pain he felt. Deb breathed out in relief before staring at her brother, concerned for him and uncertain what his next reaction would be. He remained keeled over for a few seconds before finally standing straight to look at her with concern, and a small bit of pain in his eyes, "How are you feeling?"

She stared at him in surprise. He just got beat up by her and the first thing he asks is how she's feeling. He didn't complain or anything. He was truly going to help her get better. She realized now that he would never abandon her. He would always be the one good thing in her life that wouldn't leave. Tears finally formed in her now-hopeful eyes as her lips quivered.

"Deb?" He asked in concern.

She said nothing as she suddenly wrapped her arms around him in a desperate embrace, letting her tears fall again. The front she would so often put up shattered as she let out all the sadness and grief in her as she repeated, "I love you so much!" afraid that he would somehow disappear and that she would be alone with the darkness. Dexter held her tightly against him, running his fingers through her hair comfortingly while whispering, "I'm here," again and again as he lowered them both to their knees.

He held her for what felt like an hour until she finally fell silent and stayed in his arms so long he wondered if she had fallen asleep. The thought was gone as he heard her whisper, "I can't survive without you, Dexter. I'm scared of what's gonna happen to me."

He pulled back to look at her face, "Hey, nothing's going to happen. I promise you're going to be okay. I'm never abandoning you."

She stared at him pleadingly, "You promise?" He nodded and embraced her again. She liked the sound of that. She smiled and closed her eyes, staying that way until she finally fell asleep in his arms. He noticed and placed his arms under her before carrying her to his bed, covering her with the sheet. He went to the bathroom, brushed his teeth and went back to his room. He walked to the side of the bed to stare at Deb before he looked at his shirt to see that it was ruined by her tears. He took it off before deciding to sleep on the couch.

He was surprised to feel a hand grab his arm, "No, don't leave." He stared at her before walking to the other side of the bed and laying down beside her.

Closing his eyes, Dexter relaxed his body and allowed it to sink into the soft bed. Several minutes later, he opened his eyes to look over at Debra and see her rolling over on her other side, asleep, to grab onto his arm and rest her head against his shoulder like a pillow. His hand moved to brush her hair behind her ear. She looked so peaceful. So beautiful. As if she didn't murder an innocent woman an hour ago and turned into a murderer like Dexter. He wished he could take it all back. To make it so she never walked in on him killing Travis Marshall. To make it so she didn't have to go against everything she believed in just to protect him.

She said she couldn't survive without him. Even if that may have been true, it's a guarantee that she won't survive if he stays. She never would have been ruined if he didn't exist in her life. She never would have hated herself when she should have been hating him.

But what's done is done. And he wasn't going to linger on the past. He did that before and it took him a while to pull his head out of his ass and make a difference in his life. He wasn't going to make that same mistake. He had to concentrate on protecting her. On fixing her.

He stared at the ceiling again before closing his eyes and drifting off to another dream filled with blood.

Unknown to him, Deb opened her eyes to stare at him almost dreamily before closing her eyes as well, enjoying the adjacency of their bodies. It comforted her.

 **Next Day**

Debra groaned as she woke up from a dreamless night. Her hair was disheveled and her mouth dry. She blew away a strand of hair from her mouth before she shifted and rolled over to her other side to find that Dexter was gone. She was afraid. The urge was still in her. She still felt it. Last night she had hope that he would help her, fix her. But she realized now that it was a desperate hope. A stupid one. How could he ever fix her when he couldn't fix himself?

She felt relief of the pressure on her head. But it only lasted for so long before it had now already returned. She couldn't exactly beat him up and cry in his arms every night. She had no idea what to do.

"Fuck," she whispered in despair as she covered her eyes with her hand.

She was a monster.

She suddenly heard a noise coming from the kitchen and she reluctantly got up from the bed. She walked into the kitchen to see her brother making pancakes while Harrison sat on one of the stools, excitedly and hungrily eyeing the breakfast.

The young toddler turned to see who it was that emerged from daddy's room and was surprised to see her, "Aunt Deb!"

Dexter turned his head and looked at her in surprise. She froze in surprise as she saw that his cheek had bruised before saying with genuine enthusiasm as she looked at Harrison, "Hey, buddy! How are you?" Despite everything that's happened to her, Harrison is the one thing in her life she would never have a bleak outlook upon.

"I'm hungry and daddy is making pancakes. What shape do you want yours to be? Daddy can make triangles and stars and even dragons!"

Dexter's attention returned to the pancakes, "Whoa, easy there, bud! I'm not _that_ good."

"I want whatever he's having," Debra said, nodding at Harrison. He beamed in pride.

"Stars is it, then."

Dexter dropped a few star shaped pancakes on her's and Harrison's plate before making regular ones for himself. They spent the next couple of minutes eating their pancakes while listening to Harrison talk about one of his best friends in preschool. Jaime arrived, thankfully, and took over so the two would be able to eat in peace and get to work in time. Before they left, Jaime inquired, something occurring to her, "By the way, Deb, when did you get here?"

Dexter answered, "She slept over."

"Why did you sleep in the same room, daddy?" Harrison asked with a confused look. Debra froze and felt her panic rise as Jaime looked at them in surprise.

But her brother was far calmer, "I slept on the couch."

The confused expression faded from his face as he said, "Oh." He made his way to his room to change.

Jaime had a look of realization as she smiled, "You guys can go now, I'll take care of Harrison."

"Thanks Jaime."

Dexter and Debra made their way to the parking lot before they drove to the station in silence and they finally parked in a free space. Yet none of them moved to get out of the vehicle.

Debra stared at her feet, "Dex… I can't look them in the eye. I murdered their fucking captain. I-I can't do this, I might freak out and have a panic attack!"

Dexter slowly and calmly placed his hand on hers before squeezing gently. "Listen, Deb. It's gonna be alright, I promise. I won't be going anywhere. If you're close to having a panic attack, just come to my lab, open the floodgates and let it all out on me."

She seemed to calm down as she closed her eyes and breathed. She opened them to look at him, a joking smile on her lips, yet he could see the fear and anxiousness in them, "What the fuck would I do without you, Dexter?"

' _Not be in this position, for one,_ ' he thought, but stayed silent. "Go inside. I'll be right behind you."

She seemed reluctant but complied nonetheless. He stared at her retreating form before his mind went back a few weeks. He remembered that night when she found out he'd been seeing Hannah. The night she confessed her true love for him. She was heartbroken. She accepted him for being a murderer but she didn't want to accept that he loved another woman. She pleaded and bargained for him to stop seeing her because she was afraid of losing him, afraid that he would never return her feelings the way she wanted. Her internal and emotional turmoil was evident.

He realized now how she felt. He remembered yesterday. The initial silence. Debra refused to speak at first, dead inside. Not to mention when he found out about her darkness. He was afraid of losing her love, of losing her. He pleaded and bargained too, refusing to believe that she would turn into a monster like him. He was terrified. And he put her through that when he said he wanted to be with Hannah.

But now Hannah was dead. And Deb seemed alright for now. At least when it comes to her darkness. They might just be able to make it work. Otherwise, she would've told him if she felt still the urge.

Wouldn't she?

* * *

 **Author's Note: Just a heads up for the readers of this story. This fic won't be the Season 8 Dex/Deb relationship, as in Deb won't disappear for months while blaming Dexter. I might make another fic of the kind, but this one is more of the fanfiction-y type of story without conflict between the two. At least on the subject on LaGuerta's murder. Of course, Deb won't be forgetting about what she's done. She just won't be blaming it on Dexter. *hint, hint***

 **Leave reviews and follow if you like it so far.**


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